Refrigerant compressors have become products manufactured in large numbers, and should therefore be manufactured in the most cost effective manner possible. As, however, refrigerant compressors are practically operating all the year round, the energy consumption of the motor, which is required for driving the compressor unit, must be kept as small as possible. This again requires that, for example, the rotor and the stator are assembled with the best possible mutual alignment to keep the air gap between rotor and stator small, which reduces energy losses.
U.S. Pat. No. 6,095,768 shows a refrigerant compressor with a cup-shaped stator housing, whose upper end is open. The open end is bridged by a crossover. Self-aligning bearings for the drive shaft are inserted both in the crosshead and in the bottom of the stator housing. Even though these bearings permit a certain deviation of the drive shaft from the axis of the stator, a relatively exact alignment of the crosshead must be ensured, so that the crosshead is perpendicular to the drive shaft.
Another refrigerant compressor is known from U.S. Pat. No. 3,762,837. Here, the drive shaft is supported on both sides of a crankpin arrangement. The rotor is located on the other side of a bearing. Both bearings are radially displaceable and after mounting the motor and the compressor arrangement they have to be individually aligned and fixed to ensure a uniform air gap between the rotor and the stator. For the alignment, screws are loosened and the bearings displaced. Then the screws are tightened again. Thus, the bearings are only held by means of clamping.
EP 0 524 552 A1 shows a hermetical refrigerant compressor with double-supported drive shaft, the upper bearing being fixed in a block. The lower bearing is fixed on the stator by means of a holding element, so that the rotor can align itself in relation to the stator of the motor.
In all cases, relatively accurately manufactured components are required to keep the air gap between the rotor and the stator small and to align the drive shaft perpendicularly to the bearings. A “leaning” drive shaft will eventually cause relatively heavy wear on the bearings. Further, an insufficient alignment causes frictional losses in the bearings, which again cause increased energy consumption.